Evaluation of mechanical property on fiber-matrix interface by analysis of interfacial crack propagation

Abstract

Since the fiber/matrix interface significantly affects the fracture behavior of composite materials, the interfacial properties must be properly evaluated for long-term safety of structures. Cohesive zone model has been widely used to evaluate the interfacial strength because it avoids the stress singularity along the interface by effectively including the damage process zone. Among various cohesive zone models, Ma-Kishimoto model is not only practical but also physical because it was established based on a continuum damage mechanics. In this study, material parameters of Ma-Kishimoto model are determined to evaluate fiber/matrix interface of composite material. Analytical model of boundary element method was developed for a single fiber fragmentation test, whose interfacial parameters are reduced to three parameters of initial interfacial rigidity K_t⁰, critical interface damage D_c, and critical interface separation λ_c. A boundary element method was applied to investigate the relationship between these parameters and interfacial strength t₀, interfacial fracture energy G_c, and stress distribution along interface. The numerical analysis clarified the influence of D_c on debonded length along interface under constant t₀ and G_c.